Method of controlling transmit power of ue in wireless communication system and apparatus for the same

ABSTRACT

Disclosed herein is a method of transmitting a signal at a user equipment (UE) in a wireless communication system. The method includes receiving a radio resource control (RRC) configuration message from a network; determining a preference value relating to power saving after receiving the RRC configuration message; and transmitting the determined preference value relating to the power saving to the network.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method of controlling transmit power of a userequipment (UE) in a wireless communication system and an apparatus forthe same.

BACKGROUND ART

As an example of a wireless communication system to which the presentinvention is applicable, a 3rd Generation Partnership Project (3GPP)Long Term Evolution (LTE) communication system will be schematicallydescribed.

FIG. 1 is a diagram showing a network structure of an Evolved UniversalMobile Telecommunications System (E-UMTS) as a mobile communicationsystem. The E-UMTS is an evolved form of the UMTS and has beenstandardized in the 3GPP. Generally, the E-UMTS may be called a LongTerm Evolution (LTE) system. For details of the technical specificationsof the UMTS and E-UMTS, refer to Release 7 and Release 8 of “3rdGeneration Partnership Project; Technical Specification Group RadioAccess Network”.

Referring to FIG. 1, the E-UMTS mainly includes a User Equipment (UE),base stations (or eNBs or eNode Bs), and an Access Gateway (AG) which islocated at an end of a network (E-UTRAN) and which is connected to anexternal network. Generally, an eNB can simultaneously transmit multipledata streams for a broadcast service, a multicast service and/or aunicast service.

One or more cells may exist per eNB. The cell is set to use a bandwidthsuch as 1.25, 2.5, 5, 10, 15 or 20 MHz to provide a downlink or uplinktransmission service to several UEs. Different cells may be set toprovide different bandwidths. The eNB controls data transmission orreception of a plurality of UEs. The eNB transmits downlink (DL)scheduling information of DL data so as to inform a corresponding UE oftime/frequency domain in which data is transmitted, coding, data size,and Hybrid Automatic Repeat and reQest (HARQ)-related information. Inaddition, the eNB transmits uplink (UL) scheduling information of ULdata to a corresponding UE so as to inform the UE of a time/frequencydomain which may be used by the UE, coding, data size and HARQ-relatedinformation. An interface for transmitting user traffic or controltraffic can be used between eNBs. A Core Network (CN) may include the AGand a network node or the like for user registration of the UE. The AGmanages mobility of a UE on a Tracking Area (TA) basis. One TA includesa plurality of cells.

Although wireless communication technology has been developed up to LongTerm Evolution (LTE) based on Wideband Code Division Multiple Access(WCDMA), the demands and the expectations of users and providerscontinue to increase. In addition, since other radio access technologieshave been continuously developed, new technology evolution is requiredto secure high competitiveness in the future. Decrease in cost per bit,increase in service availability, flexible use of a frequency band,simple structure, open interface, suitable User Equipment (UE) powerconsumption and the like are required.

DISCLOSURE OF INVENTION Technical Problem

An object of the present invention devised to solve the problem lies ona method of controlling transmit power of a user equipment (UE) in awireless communication system and an apparatus for the same.

Solution to Problem

The object of the present invention can be achieved by providing amethod of transmitting a signal at a user equipment (UE) in a wirelesscommunication system, including receiving a radio resource control (RRC)configuration message from a network; determining a preference valuerelating to power saving after receiving the RRC configuration message;and transmitting the determined preference value relating to the powersaving to the network.

Preferably, the RRC configuration message is a RRC configuration enquirymessage or a RRC reconfiguration message. Here, the RRC reconfigurationmessage comprising a first field that enables the UE to transmit thedetermined preference value relating to the power saving to the network.

More preferably, the determined preference value relating to the powersaving is transmitted using a RRC reconfiguration complete message or aRRC configuration response message.

More specifically, the determined preference value relating to the powersaving is included in a second field of a response message of the RRCreconfiguration message. Here, the second field may be a reason field.

Further, the UE is in a RRC connected mode.

Further, the method further comprises starting a timer upon transmittingthe determined preference value relating to the power saving to thenetwork.

Furthermore, the preference value relating to the power saving is basedon an application which is being driven in the UE. More specifically,the preference value relating to the power saving is based on latencyrequired by an application which is being driven in the UE.

As other aspect of the present invention, a method of receiving a signalat a network in a wireless communication system is disclosed. The methodcomprises transmitting a radio resource control (RRC) configurationmessage to a user equipment (UE); and receiving a preference valuerelating to power saving from the UE, wherein the preference valuerelating to the power saving is received after transmitting the RRCconfiguration message.

Preferably, the RRC configuration message is a RRC configuration enquirymessage or a RRC reconfiguration message. Here, the RRC reconfigurationmessage comprising a first field that enables the UE to transmit thedetermined preference value relating to power saving to the network.

More preferably, the preference value relating to the power saving isreceived using a RRC reconfiguration complete message or a RRCconfiguration response message. Or, the preference value relating to thepower saving is included in a second field of a response message of theRRC reconfiguration message. Here, the second field is a reason field.

More specifically, the preference value relating to the power saving isreceived from the UE after starting a timer by the UE. Or, thepreference value relating to the power saving is based on an applicationwhich is being driven in the UE. Or, the preference value relating tothe power saving is based on latency required by an application which isbeing driven in the UE.

Advantageous Effects of Invention

According to the embodiment of the present invention, it is possible toefficiently control uplink transmit power in various traffic states.

The effects of the present invention are not limited to theabove-described effects and other effects which are not described hereinwill become apparent to those skilled in the art from the followingdescription.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

In the drawings:

FIG. 1 is a diagram showing a network structure of an Evolved UniversalMobile Telecommunications System (E-UMTS) as an example of a wirelesscommunication system;

FIG. 2 is a diagram showing the concept of a network structure of anEvolved Universal Terrestrial Radio Access Network (E-UTRAN);

FIG. 3 is a diagram showing a control plane and a user plane of a radiointerface protocol architecture between a User Equipment (UE) and anEvolved Universal Terrestrial Radio Access Network (E-UTRAN) based on a3rd Generation Partnership Project (3GPP) radio access network standard;

FIG. 4 is a diagram showing physical channels used in a 3GPP system anda general signal transmission method using the same;

FIG. 5 is a diagram showing the structure of a radio frame used in aLong Term Evolution (LTE) system;

FIG. 6 is a diagram illustrating a general transmission and receptionmethod using a paging message;

FIG. 7 is a diagram showing operations of a UE and an eNB in acontention based random access procedure provided in an LTE system;

FIG. 8 is a diagram showing operations of a UE and an eNB in anon-contention based random access procedure provided in an LTE system;

FIG. 9 is a diagram showing signal flows according to an embodiment ofthe present invention; and

FIG. 10 is a block diagram of a communication apparatus according to anembodiment of the present invention.

MODE FOR THE INVENTION

The configuration, operation and other features of the present inventionwill be understood by the embodiments of the present invention describedwith reference to the accompanying drawings. The following embodimentsare examples of applying the technical features of the present inventionto a 3rd Generation Partnership Project (3GPP) system.

Although, for convenience, the embodiments of the present invention aredescribed using the LTE system and the LTE-A system in the presentspecification, the embodiments of the present invention are applicableto any communication system conesponding to the above definition. Inaddition, although the embodiments of the present invention aredescribed based on a Frequency Division Duplex (FDD) scheme in thepresent specification, the embodiments of the present invention may beeasily modified and applied to a Half-Duplex FDD (H-FDD) scheme or aTime Division Duplex (TDD) scheme.

FIG. 2 is a diagram showing the concept of a network structure of anEvolved Universal Terrestrial Radio Access Network (E-UTRAN). Inparticular, the E-UTRAN system is a system evolved from the existingUTRAN system. The E-UTRAN includes cells (eNBs) and the cells areconnected via an X2 interface. A cell is connected to a user equipment(UE) via an air interface and is connected to an evolved packet core(EPC) via an S1 interface.

The EPC includes a mobility management entity (MME), a serving-gateway(S-GW) and a packet data network-gateway (PDN-GW). The MME has accessinformation of a UE and information about capabilities of the UE. Suchinformation is mainly used for mobility management of the UE. The S-GWis a gateway having an E-UTRAN as an end point and the PDN-GW is agateway having a PDN as an end point.

FIG. 3 shows a control plane and a user plane of a radio interfaceprotocol between a UE and an Evolved Universal Terrestrial Radio AccessNetwork (E-UTRAN) based on a 3GPP radio access network standard. Thecontrol plane refers to a path used for transmitting control messagesused for managing a call between the UE and the network. The user planerefers to a path used for transmitting data generated in an applicationlayer, e.g., voice data or Internet packet data.

A physical (PHY) layer of a first layer provides an information transferservice to a higher layer using a physical channel. The PHY layer isconnected to a Medium Access Control (MAC) layer located on a higherlayer via a transport channel. Data is transported between the MAC layerand the PHY layer via the transport channel. Data is also transportedbetween a physical layer of a transmitting side and a physical layer ofa receiving side via a physical channel. The physical channel uses atime and a frequency as radio resources. More specifically, the physicalchannel is modulated using an Orthogonal Frequency Division MultipleAccess (OFDMA) scheme in downlink and is modulated using aSingle-Carrier Frequency Division Multiple Access (SC-FDMA) scheme inuplink.

A Medium Access Control (MAC) layer of a second layer provides a serviceto a Radio Link Control (RLC) layer of a higher layer via a logicalchannel. The RLC layer of the second layer supports reliable datatransmission. The function of the RLC layer may be implemented by afunctional block within the MAC. A Packet Data Convergence Protocol(PDCP) layer of the second layer performs a header compression functionto reduce unnecessary control information for efficient transmission ofan Internet Protocol (IP) packet such as an IPv4 packet or an IPv6packet in a radio interface having a relatively small bandwidth.

A Radio Resource Control (RRC) layer located at the bottom of a thirdlayer is defined only in the control plane and is responsible forcontrol of logical, transport, and physical channels in association withconfiguration, re-configuration, and release of Radio Bearers (RBs). TheRB is a service that the second layer provides for data communicationbetween the UE and the network. To accomplish this, the RRC layer of theUE and the RRC layer of the network exchange RRC messages.

One cell of the eNB is set to use a bandwidth such as 1.25, 2.5, 5, 10,15 or 20 MHz to provide a downlink or uplink transmission service toseveral UEs. Different cells may be set to provide different bandwidths.

Downlink transport channels for transmission of data from the network tothe UE include a Broadcast Channel (BCH) for transmission of systeminformation, a Paging Channel (PCH) for transmission of paging messages,and a downlink Shared Channel (SCH) for transmission of user traffic orcontrol messages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted through a downlink SCH and may alsobe transmitted through a downlink multicast channel (MCH).

Uplink transport channels for transmission of data from the UE to thenetwork include a Random Access Channel (RACH) for transmission ofinitial control messages and an uplink SCH for transmission of usertraffic or control messages. Logical channels, which are located abovethe transport channels and are mapped to the transport channels, includea Broadcast Control Channel (BCCH), a Paging Control Channel (PCCH), aCommon Control Channel (CCCH), a Multicast Control Channel (MCCH), and aMulticast Traffic Channel (MTCH).

FIG. 4 is a diagram showing physical channels used in a 3GPP system anda general signal transmission method using the same.

A UE performs an initial cell search operation such as synchronizationwith an eNB when power is turned on or the UE enters a new cell (S301).The UE may receive a Primary Synchronization Channel (P-SCH) and aSecondary Synchronization Channel (S-SCH) from the eNB, performsynchronization with the eNB, and acquire information such as a cell ID.Thereafter, the UE may receive a physical broadcast channel from the eNBso as to acquire broadcast information within the cell. Meanwhile, theUE may receive a Downlink Reference Signal (DL RS) so as to confirm adownlink channel state in the initial cell search step.

The UE which completes the initial cell search may receive a PhysicalDownlink Control Channel (PDCCH) and a Physical Downlink Shared Channel(PDSCH) according to information included in the PDCCH so as to acquiremore detailed system information (S302).

Meanwhile, if the eNB is initially accessed or radio resources forsignal transmission are not present, the UE may perform a Random AccessProcedure (RACH) (step S303 to S306) with respect to the eNB. In thiscase, the UE may transmit a specific sequence through a Physical RandomAccess Channel (PRACH) as a preamble (S303 and S305), and receive aresponse message of the preamble through the PDCCH and the PDSCHcorresponding thereto (S304 and S306). In the case of contention-basedRACH, a contention resolution procedure may be further performed.

The UE which performs the above procedures may perform PDCCH/PDSCHreception (S307) and Physical Uplink Shared Channel PUSCH)/PhysicalUplink Control Channel (PUCCH) transmission (S308) as a generaluplink/downlink signal transmission procedure. In particular, the UEreceives downlink control information (DCI) via a PDCCH. The DCIincludes control information such as resource allocation information ofthe UE and the format thereof is changed according to use purpose.

The control information transmitted from the UE to the eNB in uplink ortransmitted from the eNB to the UE in downlink includes adownlink/uplink ACK/NACK signal, a Channel Quality Indicator (CQI), aPreceding Matrix Index (PMI), a Rank Indicator (RI), and the like. Inthe case of the 3GPP LTE system, the UE may transmit the controlinformation such as CQI/PMI/RI through the PUSCH and/or the PUCCH.

FIG. 5 is a diagram showing the structure of a radio frame used in aLong Term Evolution (LTE) system.

Referring to FIG. 5, the radio frame has a length of 10 ms (327200*Ts)and includes 10 subframes with the same size. Each of the subframes hasa length of 1 ms and includes two slots. Each of the slots has a lengthof 0.5 ms (15360*Ts). Ts denotes a sampling time, and is represented byTs=1/(15 kHz*2048)=3.2552*10⁻⁸ (about 33 ns). Each slot includes aplurality of OFDM symbols in a time domain, and includes a plurality ofresource blocks (RBs) in a frequency domain. In the LTE system, one RBincludes 12 subcarriers*7(6) OFDM or SC-FDMA symbols. A TransmissionTime Interval (TTI) which is a unit time for transmission of data may bedetermined in units of one or more subframes. The structure of the radioframe is only exemplary and the number of subframes included in theradio frame, the number of slots included in the subframe, or the numberof OFDM or SC-FDMA symbols included in the slot may be variouslychanged.

Hereinafter, an RRC state of a UE and an RRC connection method will bedescribed. The RRC state indicates whether the RRC layer of the UE islogically connected to the RRC layer of the E-UTRAN, is referred to asan RRC_CONNECTED state if connected, and is referred to as an RRC_IDLEstate if not connected.

Since the E-UTRAN can check presence of the UE of the RRC_CONNETED statein cell units, it is possible to efficiently control the UE. Incontrast, the E-UTRAN cannot check presence of a UE of the RRC_IDLEstate and a core network (CN) manages the UE of the RRC_IDLE state in atracking area (TA) unit which is greater than a cell. That is, theRRC_IDLE state of the UE should transition to the RRC_CONNECTED state inorder to receive a service, such as voice or data.

In particular, when a user initially turns a UE on, the UE firstsearches for an appropriate cell and camps on the cell in an RRC_IDLEstate. When RRC connection needs to be established, the UE which is inthe RRC_IDLE state is RRC connected to the E-UTRAN via an RRC connectionprocedure so as to transition to the RRC_CONNECTED state. For example,if uplink data transmission is necessary due to call connection attemptof a user or if a response message is transmitted in response to apaging message received from the E-UTRAN, the UE which is in the idlestate needs to be RRC connected to the E-UTRAN.

FIG. 6 is a diagram illustrating a general transmission and receptionmethod using a paging message.

Referring to FIG. 6, the paging message includes a paging recordincluding a paging cause and a UE identity. When the paging message isreceived, the UE may perform discontinuous reception (DRX) for thepurpose of reducing power consumption.

More specifically, a network configures several paging occasions (POs)in every time cycle called a paging DRC cycle and a specific UE receivesonly a specific paging occasion and acquires a paging message. The UEdoes not receive a paging channel in occasions other than the specificoccasion and may be in a sleep state in order to reduce powerconsumption. One paging occasion corresponds to one TTI.

The eNB and the UE use a paging indicator (PI) as a specific valueindicating transmission of a paging message. The eNB may define aspecific identity (e.g., paging-radio network temporary identity(P-RNTI) as the PI and inform the UE of paging information transmission.For example, the UE awakes in every DRX cycle and receives one subframein order to check whether a paging message is received. If a P-RNTI ispresent in an L1/L2 control channel (PDCCH) of a subframe received bythe UE, the UE may confirm that a paging message is present in a PDSCHof the subframe. In addition, if the identity (e.g., IMSI) of the UE ispresent in the paging message, the UE responds to the eNB (e.g.,receives RRC connection or system information) and receives a servicefrom the eNB.

Next, system information will be described. The system informationincludes essential information necessary to connect a UE to an eNB.Accordingly, the UE should receive all system information before beingconnected to the eNB and always have new system information. Since allUEs located in a cell should know system information, the eNBperiodically transmits the system information.

The system information may be divided into a master information block(MIB), a scheduling block (SB) and a system information block (SIB). TheMIB enables a UE to become aware of a physical configuration of a cell,for example, a bandwidth. The SB indicates transmission information ofSIBs, for example, a transmission period. The SIB is a set of associatedsystem information. For example, a specific SIB includes onlyinformation about peripheral cells and another SIB includes onlyinformation about an uplink radio channel used by a UE.

Hereinafter, a cell selection and cell reselection process will bedescribed.

If a UE is powered on, the UE selects a cell having appropriate qualityand performs a preparation procedure for receiving a service. A UE in anRRC_IDLE state should always select appropriate quality and prepare toreceive a service from the cell. For example, a UE which is just turnedon should select a cell having appropriate quality in order to performregistration with a network. If a UE in an RRC_CONNECTED state enters anRRC_IDLE state, the UE should select a cell on which the UE will camp inthe RRC_IDLE state. A process of, at a UE, selecting a cell satisfying aspecific condition in order to camp on the cell in a service standbystate such as an RRC_IDLE state is referred to as cell selection. Sincecell selection is performed in a state in which the UE does notdetermine a cell on which the UE camps in the RRC_IDLE state, it isimportant to select a cell as fast as possible. Accordingly, a cellwhich provides radio signal quality equal to or greater than apredetermined reference may be selected in the cell selection process ofthe UE, although the cell does not provide the best radio signal qualityto the UE.

If a UE selects a cell satisfying a cell selection reference, the UEreceives information necessary for operation of the UE in an RRC_IDLEstate in the cell from system information of the cell. The UE receivesall information necessary for operation of the RRC_IDLE state and thenrequests a service from a network or a waits reception of a service fromthe network in the RRC_IDLE state.

After a UE selects a certain cell in a cell selection process, thestrength or quality of a signal between the UE and an eNB may be changeddue to mobility of the UE or wireless environment change. Accordingly,if the quality of the selected cell deteriorates, the UE may selectanother cell which provides better quality. If the cell is reselected, acell which provides better signal quality than that of a currentlyselected cell is generally selected. Such a process is referred to ascell reselection. The cell reselection process is performed in order toselect a cell which provides the best quality to the UE from theviewpoint of the quality of the radio signal. In addition to the qualityof the radio signal, the network may set priority per frequency andinform the UE of the priority. The UE which receives the prioritypreferentially takes the priority into consideration, rather than radiosignal quality.

Next, a random access (RA) procedure provided in an LTE system will bedescribed. The RA procedure provided in the LTE system is divided into acontention based random access procedure and a non-contention basedrandom access procedure. The contention based random access procedure orthe non-contention based random access procedure is determined dependingon whether a random access preamble used in the RA procedure is directlyselected by a UE or is selected by an eNB.

In the non-contention based random access procedure, the UE uses arandom access preamble which is directly allocated thereto by the eNB.Accordingly, if the eNB allocates the specific random access preambleonly to the UE, the random access preamble is used only by the UE andother UEs do not use the random access preamble. Accordingly, since therandom access preamble corresponds one-to-one to the UE which uses therandom access preamble, no contention occurs. In this case, since theeNB may become aware of the UE which transmits the random accesspreamble as soon as the eNB receives the random access preamble,efficiency is good.

In the contention based random access procedure, since a random accesspreamble is arbitrarily selected from among random access preambleswhich may be used by the UE and is transmitted, a plurality of UEs mayalways use the same random access preamble. Accordingly, when the eNBreceives a specific random access preamble, the eNB may not check whichUE transmits the random access preamble.

The UE performs the random access procedure 1) if a UE performs initialaccess without RRC connection with an eNB, 2) if a UE first accesses atarget cell in a handover process, 3) if a random access procedure isrequested by a command of an eNB, 4) if uplink data is generated in astate in which uplink time synchronization is not performed or radioresources to be used to request radio resources are not allocated and 5)upon a restoring process due to radio link failure or handover failure.

FIG. 7 is a diagram showing operations of a UE and an eNB in acontention based random access procedure provided in an LTE system.

Referring to FIG. 7, in step 701, the UE may randomly select a singlerandom access preamble from a set of random access preambles indicatedthrough system information or a handover command, and select andtransmit Physical Random Access Channel (PRACH) resources capable oftransmitting the random access preamble. At this time, the preamble iscalled RACH MSG 1.

In step 702, the UE attempts to receive its own random access responsewithin a random access response reception window indicated by the eNBthrough the system information or the handover command, after the randomaccess preamble is transmitted. More specifically, RACH MSG 2, that is,random access response information is transmitted in the form of a MACPDU and the MAC PDU is sent via a PDSCH. In addition, a PDCCH is alsosent in order to enable the UE to appropriately receive the informationsent via the PDSCH. That is, the PDCCH includes information about the UEwhich should receive the PDSCH, frequency and time information of radioresources of the PDSCH and the transmission format of the PDSCH. If theUE has successfully received the PDCCH, the random access responsetransmitted via the PDSCH is appropriately received according to theinformation about the PDCCH. The random access response includes arandom access preamble identity, UL grant, a temporary C-RNTI, a timealignment command, etc. The reason why the random access preambleidentity is necessary is because random access response information forone or more UEs may be included in one random access response and thusit is necessary to indicate for which UE the uplink grant, the temporaryC-RNTI and the time alignment command are valid. The random accesspreamble identity matches the random access preamble selected by the UEin step 701.

Subsequently, in step 703, if the UE has received the random accessresponse valid for the UE, the UE processes all information included inthe random access response. That is, the UE applies the time alignmentcommand and stores the temporary C-RNTI. In addition, data which isstored in the buffer of the UE or newly generated data is transmitted tothe eNB using the uplink grant. At this time, data transmitted via theuplink grant, that is, MAC PDU, is referred to as RACH MSG 3. Theidentity of the UE should necessarily be included in the data includedin the uplink grant. This is because the eNB may not determine which UEperforms the random access procedure in the contention based randomaccess procedure and thus should identify the UE in order to performcontention resolution later. Here, there are two different schemes forincluding the UE identity. A first scheme is to transmit the UE's cellidentity through UL grant if the UE has already received a valid cellidentity allocated by a corresponding cell prior to the random accessprocedure. Conversely, the second scheme is to transmit the UE's uniqueidentity if the UE has not received a valid cell identity prior to therandom access procedure. In general, the unique identity is longer thanthe cell identity. If the UE has transmitted data through the UL Grant,the UE starts a contention resolution (CR) timer.

Finally, after the UE transmits the data including its own identitythrough the UL Grant included in the random access response, the UEawaits an indication from the eNB for contention resolution. That is,the UE attempts to receive the PDCCH in order to receive a specificmessage. Here, there are two schemes for receiving the PDCCH. Asdescribed above, the UE attempts to receive the PDCCH using its own cellidentity if the identity transmitted via the UL Grant is a cellidentity, and the UE attempts to receive the PDCCH using the temporaryC-RNTI included in the random access response if the identity is its ownunique identity. Thereafter, in the former scheme, if the PDCCH (thatis, RACH MSG 4) has been received through its own cell identity beforethe contention resolution timer has expired, the UE determines that therandom access procedure has been normally performed and completes therandom access procedure. In the latter scheme, if the PDCCH has beenreceived through the temporary C-RNTI before the contention resolutiontimer has expired, the UE checks data transferred by the PDSCH indicatedby the PDCCH. If the unique identity of the UE is included in the data,the UE determines that the random access procedure has been normallyperformed and completes the random access procedure.

FIG. 8 is a diagram showing operations of a UE and an eNB in anon-contention based random access procedure provided in an LTE system.

As described above, in the non-contention based random access procedure,unlike the contention based random access procedure, if the randomaccess response information has been received, the UE determines thatthe random access procedure has been normally performed and completesthe random access procedure. In addition, the non-contention randomaccess procedure may be performed upon a handover process or when thisprocedure is requested by the eNB. Of course, even in these cases, thecontention based random access procedure may be performed. First, forthe non-contention based random access procedure, it is important toreceive, from the eNB, a dedicated random access preamble which may notcause contention. In order to receive the random access preamble, ahandover command and a PDCCH command may be used.

In addition, the eNB may set PRACH resources to be used when the UEtransmits the random access preamble. The PRACH resources include asubframe and frequency resources to be used when the UE transmits therandom access preamble.

Table 1 shows PRACH mask indices of PRACH resources which are set by theeNB with respect to the UE.

TABLE 1 PRACH Mask Index Allowed PRACH (FDD) Allowed PRACH (TDD) 0 AllAll 1 PRACH Resource Index 0 PRACH Resource Index 0 2 PRACH ResourceIndex 1 PRACH Resource Index 1 3 PRACH Resource Index 2 PRACH ResourceIndex 2 4 PRACH Resource Index 3 PRACH Resource Index 3 5 PRACH ResourceIndex 4 PRACH Resource Index 4 6 PRACH Resource Index 5 PRACH ResourceIndex 5 7 PRACH Resource Index 6 Reserved 8 PRACH Resource Index 7Reserved 9 PRACH Resource Index 8 Reserved 10 PRACH Resource Index 9Reserved 11 Every, in the time domain, Every, in the time domain, evenPRACH opportunity even PRACH opportunity 1^(st) PRACH Resource Index1^(st) PRACH Resource Index in subframe in subframe 12 Every, in thetime domain, Every, in the time domain, odd PRACH opportunity odd PRACHopportunity 1^(st) PRACH Resource Index 1^(st) PRACH Resource Index insubframe in subframe 13 Reserved 1^(st) PRACH Resource Index in subframe14 Reserved 2^(nd) PRACH Resource Index in subframe 15 Reserved 3^(rd)PRACH Resource Index in subframe

For example, in the FDD mode, the UE may transmit the random accesspreamble in one subframe or even subframes or odd subframes among 10subframes according to the PRACH mask indices of Table 1.

Referring to FIG. 8, the UE receives a random access preamble allocatedby the eNB in step 801 and transmits the preamble to the eNB in step802. A method of receiving a random access response in step 803 is equalto that of the contention based random access procedure of FIG. 7.

Recently, in an Internet environment, traffic is bi-directionallygenerated. That is, for example, in a smart phone, a packet transmittedto a network and a packet transmitted from a network to a smart phoneare present. If a smart phone, that is, a UE, generates a packet, the UEimmediately accesses the network and requests that the network allocateradio resources so as to inform an eNB that the UF has data to betransmitted to the eNB. Therefore, there is no problem in packettransmission.

However, if the network generates data, the UE may not automaticallyrecognize that the network generates the data. Accordingly, the UEdetermines whether there is data transmitted from the network to the UEusing a signal transmitted from the network. In this case, if the UEcontinuously checks data to be received, a large amount of power isconsumed. Accordingly, the UE checks data to be received atpredetermined periods according to network configuration and thischecking procedure is referred to as a discontinuous reception (DRX)procedure.

According to a DRX procedure, the network may confirm when the UE maymonitor the signal of the network. At this time, the network may informthe UE that there is data to be transmitted if necessary. Here, the DRXcycle is defined and the DRX cycle sets at which time interval the UEmonitors the signal of the eNB. For example, if the DRX cycle is 1second, the UE monitors the signal of the eNB at a time interval of 1second.

Only UEs having a simple function were present in the past. Such UEs didnot have an Internet access function and provided a simple informationdisplay function although the Internet access function is present.However, as smart phones have rapidly come into widespread use, the UEmay access the Internet at anytime and support new and variousapplications through Internet access. Each application may operate andgenerate traffic even when a user does not directly manipulate the UE,and, in some cases, different applications may simultaneously generatetraffic. Conventionally, each UE prepared only for incoming voice call.However, in a smart phone environment, each UE should prepare fortraffic which may be transmitted from the Internet to each applicationat anytime.

Examples of traffic mainly generated under a current smart phoneenvironment may include traffic generated in an Internet browsingprocess, traffic generated in an application such as a shooting game,traffic generated in an application such as instant messaging andtraffic generated in an application such as Voice over Internet Protocol(VoIP).

In case of traffic generated in an Internet browsing process, anInternet page starts to be loaded after a user clicks on a web browser,and the user starts to read content if page loading has been completed.New Internet data is not displayed until the user clicks a certain linkon an Internet page. Even when a time required for loading a page afterclicking is as long as several seconds, the user does not havecomplaints. Even in instant messaging, since it takes considerable timefor a user to input text under a smart phone, instantaneous messagetransmission is not required.

On the contrary, in case of VoIP, voice data of a user should beimmediately transmitted to a counterpart and a network and voice data ofa counterpart should be immediately transmitted to a user. Forreference, in case of a voice call application, voice data is generatedone by one at intervals of 20 ms.

In consideration of traffic characteristics, a DRX cycle of Internetbrowsing or instant messaging is preferably long. However, a DRX cycleof VoIP is preferably short. Here, when the eNB sets the DRX cycle ofthe UE, the eNB does not know which application is installed in the UEor which application is currently being activated. In particular, sincea DRX procedure is not performed with respect to data generated by theUE but is performed with respect to downlink data transmitted from theInternet to the UE, the eNB should set parameters associated with theoverall DRX procedure including a DRX cycle suitable for the UE beforetraffic arrives from the Internet.

Even when the eNB sets DRX parameters optimized for Internet browsingwith respect to the UE, if the UE actually performs VoIP, delay occursin voice transmission and thus user satisfaction is poor. If DRXparameters optimized for VoIP are set with respect to a user who usesInternet browsing, battery charge may be rapidly drained. DRX parametersare defined in “DRX-Config” of the 3GPP standard document TS36.331 andinclude a DRX cycle length, a DRX cycle offset, a DRX inactivity timer,a DRX retransmission timer, etc. If the UE actually establishesconnection with the eNB, the DRX configuration information istransmitted to the UE via “RadioResourceConfigDedicatedIE” of the 3GPPstandard document TS36.331.

In summary, power consumption has been rapidly increased due toinfluence of a new traffic environment, thereby decreasing usersatisfaction. Accordingly, in the present invention, in an environmentin which various applications for generating data having differentcharacteristics are installed, it is possible to reduce powerconsumption of a UE and increase user satisfaction by providing a datatransfer service having appropriate quality.

In the present invention, a UE collects traffic environment informationused to set parameters in order to manage connection between the UE andan eNB and transmits the traffic environment information to the eNB.Here, the traffic environment information may include content shown inTable 2. The traffic environment information is transmitted from the UEto the network in association with power consumption of the UE and thusmay be referred to as power preference information.

TABLE 2 —Information as to whether the screen of the UE is turnedon—Information as to whether there is location information of theUE—Location information of the UE—Information as to whether anapplication/service of the UE generates data—Information as to whetheran application/service displayed on the screen of the UE generatesdata—Number of applications/services which are currently activated inthe UE—Information as to whether an application/service sensitive todelay is activated—Information as to whether a GPS is turnedon—Information about the velocity of the UE—Information as to whetherthe UE is moving or stationary—Traffic characteristic information—Powerinformation of the UE—Information as to how much power is left in thebattery of the UE—Information about power recently used for apredetermined time—Information as to whether the UE is connected to apower source—User preference information

If the eNB becomes aware of the information about the velocity of the UEaccording to the traffic environment information of Table 2, the eNB mayaccurately determine whether the UE is in an RRC_CONNECTED state or anRRC_IDLE state, by taking presence of user data into consideration.

For example, a UE having a high velocity does not use a handover processbut first enters an RRC_IDLE state and then transitions to anRRC_CONNECTED state in a new cell. In this case, the UE may use thefollowing method in order to transmit velocity information to the eNB.First, the eNB sends velocity band information to the UE. For example,velocity band 1 is from 0 km/h to 30 km/h and velocity band 2 is from 30km/h to 60 km/h. Thereafter, the UE measures the velocity thereof andinforms the eNB that the velocity corresponds to velocity band 1, if thevelocity of the UE corresponds to velocity band 1. Thereafter, if thevelocity of the UE is changed and thus the velocity band is changed, theUE informs the eNB that the velocity is changed.

As another implementation of the velocity information, the UE informsthe eNB of information indicating through how many cells the UE movesduring a predetermined time when the UE transitions from the RRC_IDLEstate to the RRC_CONNECTED state. For example, if the UE moves throughthree cells for 10 seconds, the velocity of the UE is regarded as beingfaster than the velocity of the UE which moves through one cell during10 seconds. In this case, the eNB releases RRC connection of the UEhaving a high velocity as soon as data transfer is finished and preventa handover operation of the UE, thereby preventing additional powerconsumption of the UE. Alternatively, when the UE transitions from theRRC_IDLE state to the RRC_CONNECTED state, information indicating whentraffic has been finally generated in the UE and exchanged with thenetwork may be transmitted to the eNB.

The traffic characteristic information of Table 2 is calculated inconsideration of an application installed in the UE, an applicationactivated in the UE, traffic generated in the UE, etc. The trafficcharacteristic information of the UE may include 1) distribution and/oraverage value of the sizes of traffic packets, 2) distribution and/oraverage value of inter-arrival time values of traffic packets, 3) TCPprotocol stack information, for example, information as to whether a TCPtimeout value, a TCP buffer size or a delayed ACK mechanism is used.When the traffic characteristic information is generated, the UE maytake an Internet Protocol (IP) layer and operation of a lower radioprotocol layer into consideration and thus may take data transmissiondue to an RLC status PDU such as RLC ACK into consideration.

In Table 2, user preference information refers to information indicatingwhether the UE requires low latency or high battery saving. For example,since latency should be minimized in case of VoIP, a short DRX cycle isrequired and, at this time, the UE consumes a large amount of power. Onthe contrary, since latency is not problematic in case of an instantmessaging service, a long DRX cycle is used and thus power consumptionis advantageously reduced. Accordingly, the UE informs the eNB ofinformation as to whether a DRX cycle, in which a large amount of poweris consumed but latency is short, is desired to be set through userselection or UE calculation. In other words, the UE informs the eNB ofinformation as to whether a DRX cycle, in which a small amount of poweris consumed but latency is long, is desired to be set through userselection or UE calculation. A method of sending the user preferenceinformation from the UE to the eNB may be implemented as follows.

First, the UE stores first configuration information and secondconfiguration information with respect to DRX configuration information,selects one of the first configuration information and the secondconfiguration information in consideration of a traffic state thereof,and informs the eNB of the selected information.

Alternatively, the UE may store only first configuration informationwith respect to DRX configuration information and inform the eNB whetherthe DRX configuration information is requested to be changed from thefirst configuration information in consideration of a traffic statethereof. An example of the first configuration information is first DRXconfiguration information transmitted by the UE. Alternatively, thefirst configuration information refers to configuration informationassociated with DRX specified by the eNB as the first configurationinformation when the eNB transmits DRX configuration information to theUE. Alternatively, the first configuration information refers to DRXconfiguration information transmitted from the eNB to the UE immediatelybefore the eNB transmits DRX configuration information to the UE.Alternatively, the first configuration information may refer to DRXconfiguration information which is set and used by the UE when the eNBtransmits DRX configuration information to the UE.

More specifically, if the UE does not use the first configurationinformation or if the UE sets the DRX cycle according to secondconfiguration information, the UE may transmit the user preferenceinformation and request to set a DRX cycle according to the firstconfiguration information.

Alternatively, when the UE sets the DRX cycle according to the firstconfiguration information, the UE transmits the user preferenceinformation to the eNB and requests that the eNB set the DRX cycleaccording to the second configuration information, differently from thefirst configuration information.

The user preference information is used to inform the eNB as to whetherthe UE uses a long DRX cycle or whether the UE desires to transition tothe RRC_IDLE state to transition to a battery saving state.

The user preference information, that is, information as to whether theUE requires low latency or high battery saving is sent from the UE tothe eNB in association with power consumption and thus may be referredto as power preference indicator.

In addition, the user preference information may be transmitted to theeNB as follows. The UE transmits the user preference information to theeNB if currently set DRX configuration information is not satisfied. Theuser preference information transmitted at this time is relativeinformation indicating whether the UE desires to set the DRX cycle inwhich power consumption is higher than the currently used DRX cycle butlatency is low or whether the UE desires to set the DRX cycle in whichpower consumption is lower than the currently used DRX cycle but latencyis high. Preferably, since only information about whether powerconsumption is increased or decreased or the DRX cycle is increased ordecreased as compared to the currently set DRX cycle is indicated, thisinformation may be represented using 1 bit.

However, in the above process, the traffic characteristic informationmay be calculated by the UE and transmitted to the network or may bedirectly calculated by the network. Packets transmitted from the UE tothe network may be sent from the UE to a core network via a base station(eNB). Similarly, packets transmitted from the network to the UE may betransmitted via a core network and an eNB. Accordingly, if transmissionlatency and loss generated between the eNB and the UE is ignored,traffic transmission information calculated at the UE and trafficcharacteristic information calculated at each node of the network aresimilar. Accordingly, in another embodiment of the present invention,traffic characteristic information is calculated and specified by thenetwork, such as PCRF/S-GW/-P-GW/eNB/MME.

In this case, while the UE is in the RRC_CONNECTED state, the networkanalyzes traffic exchanged with the UE, calculates trafficcharacteristic information, and stores the information. Preferably, whenthe UE transitions to the RRC_IDLE state, the traffic characteristicinformation generated when the UE is in the RRC_CONNECTED state isstored in the network. Thereafter, if the UE transitions to theRRC_CONNECTED state again, the stored information is sent to the eNBagain and the eNB sets parameters necessary for connection to the UEusing the received traffic characteristic information. In this case, thetraffic characteristic information is a previously used DRXconfiguration or optimal DRX configuration which is stored throughprevious traffic analysis or setting value analysis.

In order to more efficiently set parameter values necessary forconnecting the UE and the eNB, UE connection configuration informationmay be stored in addition to the DRX configuration value. That is, thenetwork may store connection configuration information which has beenused for recent access when the UE enters the RRC_IDLE state andestablish connection with the UE using the stored information when theUE enters the RRC_CONNECTED state again.

The above-described traffic environment information and trafficcharacteristic information define an RRC connection configurationenquiry message, an RRC connection configuration suggestion message andan RRC connection configuration rejection message. For example, the UEreceives new connection configuration information from the eNB, analyzesthe connection configuration information, and informs the eNB of aparameter capable of improving capabilities or power consumption thereofvia an RRC connection configuration suggestion message if present.

At this time, in order to prevent the UE from arbitrarily transmittingan RRC configuration suggestion message, the UE sends an RRC suggestionmessage or an RRC configuration rejection message to the network onlywhen the network sends an RRC configuration enquiry message orinformation corresponding thereto. The RRC configuration rejectionmessage informs the network that some parameters included in newconnection configuration information transmitted from the network to theUE may cause problems in capabilities of the UE.

The UE may include information as to which parameter causes problems ora reference value of the parameter when sending the RRC configurationsuggestion message or the RRC configuration rejection message.Additionally, when the UE transmits the RRC configuration suggestionmessage or the RRC configuration rejection message to the eNB, the UEmay further include cause information indicating why the message issent. The cause information field includes information indicating thatpower of the UE is insufficient or an application of the UE requires lowlatency.

As another example, when eNB wants to know UE's preferred configuration,it sends RRC Configuration Enquiry message to UE. When a UE receives aRRC Configuration Enquiry message, the UE responds with RRCConfiguration Response message. If the UE wants to changeRRC/PDCP/MAC/RLC/PHY configuration, the RRC Configuration Responsemessage includes the preferred value of the parameter that the UE wantsto change.

Further, a RRC Reconfiguration message can include a field RRCSuggestion field. When a UE receives a RRC message including ‘RRCSuggestion field’ set to ‘yes’, and if the UE have a parameter that itwants to change, the UE responds with preferred value for the parameterin the RRC reconfiguration complete or the RRC Configuration Responsemessage. In this case, if the reason to change is to save power, the UEfurther include the reason field in the response message.

Furthermore, when the RRC message including the preferred value for theparameter such as the Power indicator is transmitted, the UE runs atimer X. Alternatively, this timer can be started when the acknowledgeof successful transmission is received in the lower layer.Alternatively, this timer can be started when the new DRX setting isreceived from the network. While this timer is running, the UE shouldnot transmit another RRC message including the preferred value for theparameter such as the Power indicator Power Indicator. Preferably, ifthe setting of Power indicator change or UE preference change while thetimer X is running, the UE sends another power indicator and timer X isrestarted.

In addition, the traffic environment information and the trafficcharacteristic information may be transmitted using a MAC controlelement in order to reduce overhead of the RRC message. In this case,the MAC control element may use a specific logical channelidentification (LCID) value. Such MAC control element may include DRXconfiguration information preference of the UE.

In addition, even when the UE transmits the above-described trafficenvironment information and traffic characteristic information to theeNB, a specific eNB may not perform a function for processing thetraffic environment information and traffic characteristic information.In this case, if the UE transmits the traffic environment informationand traffic characteristic information to the eNB, this leads to radioresource waste and eNB malfunction.

Accordingly, in the present invention, the eNB informs the UE whetherthe eNB may perform a function associated with the traffic environmentinformation and traffic characteristic information. The UE may informthe eNB as to whether the UE may perform a function associated with thetraffic environment information and traffic characteristic information.In addition, if the eNB informs the UE as to whether the eNB may performa function associated with the traffic environment information andtraffic characteristic information, the UE may inform the eNB as towhether the UE may perform a function associated with the trafficenvironment information and traffic characteristic information.

If the eNB uses the traffic environment information or trafficcharacteristic information according to the present invention, the eNBprovides appropriate connection configuration information to the UE ofthe user so as to use an appropriate DRX cycle or release RRC connectionto the UE at an appropriate time to switch the UE to the RRC_IDLE state.Accordingly, it is possible to optimize power consumption of the UE andappropriately control latency. According to the present invention, whena mobile communication system efficiently sets a system configurationvalue, the UE efficiently measures and reports support information so asto reduce power consumption of the UE and to provide appropriate servicequality to the user.

FIG. 9 is a diagram showing signal flows according to an embodiment ofthe present invention.

Referring to FIG. 9, the UE receives the RRC configuration message fromthe network such as eNB in S901. Here, the RRC configuration message canbe a RRC configuration enquiry message or a RRC reconfiguration message.Preferably, the RRC reconfiguration message comprises a field thatenables the UE to transmit a preference value relating to power savingto the network.

The UE, which receives the RRC configuration message, determines thepreference value relating to the power saving in S902. That is, the UEdetermines the preference value relating to the power saving afterreceiving the RRC configuration message from the network.

Preferably, the preference value relating to the power saving isdetermined in consideration of an application which is being driven inthe UE. More specifically, the preference value relating to the powersaving is determined according to latency required by the application.

Further, the UE transmits the preference value relating to the powersaving to the network in S903. Here, the preference value relating tothe power saving is transmitted using a RRC reconfiguration completemessage or a RRC configuration response message. Preferably, thepreference value relating to the power saving is included in a reasonfield of the RRC reconfiguration complete message or of the RRCconfiguration response message.

More preferably, the UE can start a timer starting a timer upontransmitting the determined preference value relating to the powersaving to the network. While this timer is running, the UE should nottransmit another RRC message including the preference value relating tothe power saving.

FIG. 10 is a block diagram of a communication apparatus according to anembodiment of the present invention.

Referring to FIG. 10, a communication apparatus 1000 includes aprocessor 1010, a memory 1020, a Radio Frequency (RF) module 1030, adisplay module 1040 and a user interface module 1050.

The communication apparatus 1000 is shown for convenience of descriptionand some modules thereof may be omitted. In addition, the communicationapparatus 1000 may further include necessary modules. In addition, somemodules of the communication apparatus 1000 may be subdivided. Theprocessor 1010 is configured to perform an operation of the embodimentof the present invention described with respect to the drawings. For adetailed description of the operation of the processor 1010, referencemay be made to the description associated with FIGS. 1 to 9.

The memory 1020 is connected to the processor 1010 so as to store anoperating system, an application, program code, data and the like. TheRF module 1030 is connected to the processor 1010 so as to perform afunction for converting a baseband signal into a radio signal orconverting a radio signal into a baseband signal. The RF module 1030performs analog conversion, amplification, filtering and frequencyupconversion or inverse processes thereof. The display module 1040 isconnected to the processor 1010 so as to display a variety ofinformation. As the display module 1040, although not limited thereto, awell-known device such as a Liquid Crystal Display (LCD), a LightEmitting Diode (LED), or an Organic Light Emitting Diode (OLED) may beused. The user interface module 1050 is connected to the processor 1010and may be configured by a combination of well-known user interfacessuch as a keypad and a touch screen.

The above-described embodiments are proposed by combining constituentcomponents and characteristics of the present invention according to apredetermined format. The individual constituent components orcharacteristics should be considered to be optional factors on thecondition that there is no additional remark. If required, theindividual constituent components or characteristics may not be combinedwith other components or characteristics. Also, some constituentcomponents and/or characteristics may be combined to implement theembodiments of the present invention. The order of operations to bedisclosed in the embodiments of the present invention may be changed.Some components or characteristics of any embodiment may also beincluded in other embodiments, or may be replaced with those of theother embodiments as necessary. Moreover, it will be apparent that someclaims referring to specific claims may be combined with other claimsreferring to the other claims other than the specific claims toconstitute the embodiment or add new claims by means of amendment afterthe application is filed.

The above-mentioned embodiments of the present invention are disclosedon the basis of a data communication relationship between a base stationand a user equipment. Specific operations to be conducted by the basestation in the present invention may also be conducted by an upper nodeof the base station as necessary. In other words, it will be obvious tothose skilled in the art that various operations for enabling the basestation to communicate with the user equipment in a network composed ofseveral network nodes including the base station will be conducted bythe base station or other network nodes than the base station. The term“Base Station” may be replaced with the terms fixed station, Node-B,eNode-B (eNB), or access point as necessary.

The embodiments of the present invention can be implemented by a varietyof means, for example, hardware, firmware, software, or a combinationthereof. In the case of implementing the present invention by hardware,the present invention can be implemented through application specificintegrated circuits (ASICs), digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs),field programmable gate arrays (FPGAs), a processor, a controller, amicrocontroller, a microprocessor, etc.

If operations or functions of the present invention are implemented byfirmware or software, the present invention can be implemented in theform of a variety of formats, for example, modules, procedures,functions, etc. The software code may be stored in a memory unit so asto be driven by a processor. The memory unit may be located inside oroutside of the processor, so that it can communicate with theaforementioned processor via a variety of well-known parts.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

INDUSTRIAL APPLICABILITY

Although an example of applying a method of controlling transmit powerof a user equipment (UE) in a wireless communication system and anapparatus for the same to a 3GPP LTE system is described, the presentinvention is applicable to various wireless communication systems inaddition to the 3GPP LTE system.

1-20. (canceled)
 21. A method of transmitting a signal at a userequipment (UE) in a wireless communication system, the methodcomprising: receiving a radio resource control (RRC) configurationmessage from a network, wherein the RRC configuration message comprisesa first field that enables the UE to transmit to the network apreference value relating to power saving; determining a firstpreference value relating to the power saving after receiving the RRCconfiguration message; transmitting the determined first preferencevalue relating to the power saving to the network, if the determinedfirst preference value relating to the power saving is different from asecond preference value relating to the power saving which wastransmitted last to the network.
 22. The method of claim 21, wherein theRRC configuration message is a RRC configuration enquiry message or aRRC reconfiguration message.
 23. The method of claim 21, wherein thedetermined first preference value relating to the power saving istransmitted using a RRC reconfiguration complete message or a RRCconfiguration response message.
 24. The method of claim 21, wherein thedetermined first preference value relating to the power saving isincluded in a second field of a response message of the RRCreconfiguration message.
 25. The method of claim 24, wherein the secondfield is a reason field.
 26. The method of claim 21, wherein the UE isin a RRC connected mode.
 27. The method of claim 21, wherein the firstpreference value relating to the power saving is based on an applicationwhich is being driven in the UE.
 28. A method of receiving a signal at anetwork in a wireless communication system, the method comprising:transmitting a radio resource control (RRC) configuration message to auser equipment (UE), wherein the RRC configuration message comprises afirst field that enables the UE to transmit to the network a preferencevalue relating to power saving; and receiving a first preference valuerelating to the power saving from the UE, wherein the first preferencevalue relating to the power saving is different from a second preferencevalue relating to the power saving which was received last from the UE.29. The method of claim 28, wherein the RRC configuration message is aRRC configuration enquiry message or a RRC reconfiguration message. 30.The method of claim 28, wherein the first preference value relating tothe power saving is received using a RRC reconfiguration completemessage or a RRC configuration response message.
 31. The method of claim28, wherein the first preference value relating to the power saving isincluded in a second field of a response message of the RRCreconfiguration message.
 32. The method of claim 31, wherein the secondfield is a reason field.
 33. The method of claim 28, wherein the UE isin a RRC connected mode.
 34. The method of claim 31, wherein the firstpreference value relating to the power saving is based on an applicationwhich is being driven in the UE.